When a husband uses drugs, he abandons his wife, he abandons his children. It is my understanding that the church does not support husbands who abandon their families. When a husband walks away from his family, then according to scripture, it is my understanding that then the church community becomes "husband" and "father" to the abandoned wife and children who now need support. The husband, having turned his back on his family and on the church, is on his own, by his own free will.
The sermon you heard: the salvation of the husband came from God and not from the wife. Wives do not save their husbands. A man's life is in God's hands and no one else's. It would be ego-inflation if any one of us thought we could be the person to transform someone's life. That is always between the individual and God.
If and when your husband has a real relationship with God and in both word and deed and consistently over a long period of time has demonstrated this new relationship with God through sobriety and amends, that is when you could once again put on your wedding rings.
As for the drug deal: methadone (if he is actually on it) relates only to opiate addiction. It does not affect the use of other mind-altering substances. He can get high in other ways, if he chooses to.